The present invention relates to a fixing unit which is used in a copying machine or a printer using toner to fix a toner image, and an image forming apparatus in which the fixing unit is incorporated.
A fixing unit is incorporated in a copying machine which uses an electrophotographic process, to heat and melt a developer or toner formed on a member to be fixed, for example, paper material (non-processed paper), to fix the toner to the piece of paper (paper material). As a well-known method of heating a toner usable in a fixing unit, there is a method of using radiant heat obtained by lighting a filament lamp or a halogen lamp, and a flash heating method using a flash lamp as a heating source. In recent years, a fixing unit which uses an induction heater as a heating source has also been put to practical use. A fixing unit using an induction heater can reduce the time required to heat a heating (fixing) roller or sheet up to a temperature for melting the toner.
In many cases, a heating roller containing a heater inside and a pressing roller pressed by a predetermined pressure to a heating roller or sheet at one point on its outer circumference, are used. In this structure, it is easy to efficiently supply the heat from a heat source to the toner, and to supply a pressure for fixing a melted toner to a piece of paper.
When an induction heater is used as a heat source, a current flowing in an excitation coil reaches several tens of amperes. Thus, when disconnecting the fixing unit or sliding it toward the front of a copying machine by a sliding mechanism to clear a paper jam, or when opening the cover or the like, the power supply to the induction heater must be interrupted. When the power supply to the induction heater cannot be interrupted by a structure, a cover or the like is separately provided to disable the user or operator from touching a current-carrying part.
However, if the unit is constructed to interrupt the power to the induction heater when removing or sliding the fixing unit or opening the cover for maintenance, for example, a drawer connector which can release electrical connection when being slid is used, and a problem of lowering a contact resistance through long-term use rises. This will cause an electrical short-circuit or other defects.
Further, provision of a cover to prevent the user or operator from touching a current-carrying part raises another problem that the shape and structure of the additional cover becomes complex. The additional cover requires an additional cost. If the current-carrying part is formed difficult to be touched by the user or operator, it will be difficult to clear a paper jam, or extremely decrease the workability in maintenance.
It is an object of the present invention to provide a fixing unit and an image forming apparatus, which make it difficult for the user or operator to touch a current-carrying part, and increase the workability in clearing a paper jam and maintenance.
The present invention provides an apparatus which forms an image, comprising:
a recording medium carrying mechanism which carry a material to be transferred and permits fixing of a visualizing agent adhered selectively to an electrostatic image formed on a latent image bearing member, and which move to a predetermined position together with a sliding mechanism;
a recording medium heating unit which supplies a predetermined heat and pressure to the material to be transferred, to which the visualizing agent has been transferred, and the visualizing agent, respectively, and fixes the visualizing agent to the material to be transferred, the recording medium heating unit including a first member made of a material in which an eddy current to be generated, a second member capable of supplying a predetermined pressure to the first member, and a magnetic field generating unit which generates a magnetic field to generate an eddy current in the first member, the recording medium heating unit movable to a predetermined position;
a magnetic field generating unit driving mechanism which supplies a predetermined high-frequency output to the magnetic field generating unit to enable the unit to generate a magnetic field;
a commercial power supply mechanism which supplies a predetermined power used by the magnetic field generating unit driving mechanism to supply the predetermined high-frequency output to the magnetic field generating unit; and
an electrical connection mechanism which can interrupt the power from the commercial power supplying mechanism to the magnetic field generating unit driving mechanism, between the commercial power supplying mechanism and the magnetic field generating unit driving mechanism.
The present invention provides an image forming apparatus comprising:
a photoconductor which is selectively exposed with light in the state being electrified to a predetermined electric potential, and holds the potential difference between an exposed part exposed with light and a non-exposed part not exposed with light as a latent image;
a developing unit which supplies toner to the latent image formed on the photoconductor, and makes the image visible;
a recording medium carrying mechanism which carry a recording medium capable of holding the toner non-electrostatically to the photoconductor, and can move to a predetermined position together with a sliding mechanism;
a transfer unit which electrostatically draws the toner to the recording medium carried by the recording medium carrying mechanism toward the photoconductor;
a fixing unit which supplies the recording medium, to which the toner has been transferred by the transfer unit, and the toner, respectively, and fixes the toner to the recording medium, the fixing unit including a first member made of a material in which an eddy current to be generated, a second member capable of supplying a predetermined pressure to the first member, and an excitation circuit which generates a magnetic field to generate an eddy current in the first member, the fixing unit movable to a predetermined position together with a sliding mechanism;
an excitation circuit control unit which sets the frequency of a high-frequency output that the excitation circuit has to output to generate the magnetic field;
a commercial power supply mechanism which supplies a predetermined power used by the excitation circuit control unit to supply the predetermined high-frequency output to the excitation circuit;
a slide type connector which includes a contact and a terminal, and interrupt the power supply from the commercial power supplying mechanism to the excitation circuit control unit, between the commercial power supplying mechanism and the excitation circuit control unit, the contact fixed to a predetermined position in the fixing unit, the terminal fixed to the side where the predetermined power is supplied to the commercial power supplying mechanism; and
a cover member which covers the excitation circuit provided in the fixing unit as one body, the cover member openable only when the recording medium carrying mechanism moves to a predetermined area, and while the cover member is being opened, the recording medium carrying mechanism cannot return to the original position.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.